Some people wear glasses to help them to see clearly. Even if you have very good eyesight, some things in our world are so small or so far away that you will need help to seem them. Astronomers use telescopes to observe distant stars or details of the surface of the Moon and planets.

Binoculars help bird watchers identify birds high in a tree. Using microscopes scientists can see things that are invisible to the naked eye, such as the details of this bread mould.

Microscopes

Small things need to be magnified or made bigger so that they become visible to us. Scientists use microscopes to do this. Objects that can be seen using a microscope are described as microscopic.

Light microscopes are used in schools and many laboratories.

Light from a mirror or a lamp passes through a specimen or object. The specimen being looked at must be very thin so that the light can pass through it easily. The light then passes through a series of lenses that causes the specimen to appear bigger. What you see through the microscope is called the image.

Stereo microscopes

Stereo microscopes are like using two monocular (one eyed) microscopes joined together. Just like our eyes the two eye pieces focus on the same point from different angles.

The most important difference you must know between the Monocular and binocular microscopes versus the stereo microscopes is that mocular/binocular microscopes focus on a SINGLE POINT AT THE SAME ANGLE whereas the stereo microscope focuses on a SINGLE POINT AT 2 DIFFERENT ANGLES.

The light source from stereo microscopes may be lamps or reflected light from the Sun.

When you move a specimen under a stereo microscope, the image moves the same way. That is, you move the specimen to the right and the image also moves to the right.

Magnification

The magnification of the microscope tells how much bigger the image is than the real object.

• A magnification of x10 (times ten) means the image is 10 times bigger.
• As the magnification increases, the amount of the specimen you can see (the field of view) gets smaller.
• The maximum magnification achieved by light microscopes is about x1000. At this magnification, some of the largest bacteria are just visible.

Very small measurements

Many of the objects observed using a microscope are smaller than the full stop and so they must be measured in units smaller than a millimeter.

A micrometer (μm) is one-thousandth of a millimeter, or one-millionth of a meter. It is the unit most often used by scientists to measure microscopic objects.

Electron microscopes

Electron microscopes are much more powerful than light microscopes. These microscopes use beams of tiny particles called electrons instead of light, are able to magnify up to a million times.

There are two types of electrons microscopes:

1. Transmission electron microscopes (TEM)
2. Scanning electron microscopes (SEM)